Submersible pumps are used in many different application and industries. A submersible pump has an electric motor disposed within a liquid tight housing with a drive shaft of the motor extending from the housing. An impeller is connected to the shaft and disposed within a pump casing. The casing has an inlet through which fluid is drawn into the pump. When the submersible pump is submersed in or otherwise lowered into a body of fluid and operated, the fluid is drawn into the inlet and directed to an outlet via the action of the motor and impeller. A hose may be connected to the outlet of the pump to channel the fluid to a remote location or tank.
In the context of this specification including the Claims the term “submersible pump”, is intended to include, but is not limited to, a semi-submersible pump or any pump which is required to be at least partially submersed in a liquid in order for a suction side of the pump to draw the liquid.
In some applications solid matter is contained in the fluid to be pumped. To reduce clogging and damage to the pump a strainer can be provided up stream of the inlet. The strainer acts to impede and indeed prevent the passage of the solid matter of a size larger than the “mesh size” of the strainer from entering the inlet. The strainer can form a peripheral wall of chamber at a bottom end of the pump within which the inlet is disposed. The bottom end may be open or covered by the strainer. In the event of an open bottom, the bottom of chamber can in use be substantially closed by resting the bottom of the chamber on a submerged surface.
To provide context in one example submersible pumps are sometimes used to dewater excavations during and following the application of shotcrete. It is known for shotcrete to include or incorporate metal reinforcing fibres or strands. During the dewatering process these fibres or strands normally do not cause any significant problems in relation to the operation of the pump. The reason for this is that the specific gravity of the fibres or strands is such that they tend to settle at the bottom and are not drawn in or picked up by the flow of water through the inlet or strainer when provided.
However, it is becoming more common to utilise, in shotcrete, reinforcing strands or fibres having a specific gravity less than that of water. For example fibre glass strands. These are entrained in and carried by the water being drawn in to the inlet by the impeller. The provision of a strainer as described above is intended to prevent this from occurring. But in practise the strainer becomes rapidly blocked. Further while these fibres are relatively long they are very narrow and therefore many pass through the strainer and the inlet into the pump casing. This causes substantial damage and ultimately, if not detected early, failure of the submersible pump.
The above discussion is not intended to limit the application of the submersible pump and method of pumping as disclosed herein.